Another "tile over asbestos tile" question (w/ pics)

I'm remodeling the kitchen in my 1946 house. One of the next steps (if all goes as planned) is to lay some 12x12" porcelain tile. Unfortunately, the existing flooring appears, to my untrained eye, to be 9x9" vinyl-asbestos tile. I've also heard that the mastic used to adhere the tile may contain asbestos.

Complicating this situation, I currently have 4 different layers of flooring in various areas that all need to be brought up to the same level before the new tile goes in. Starting from the bottom, there's a wood subfloor (basement below), 3/4" tongue & groove douglas fir, then 1/8" underlayment, then 1/8" vinyl-asbestos tile.

Here's the current situation:

I should note that while almost all of the tile seems well-adhered to the underlayment (seems to be masonite or luan), there are a few whole tiles or cut tiles that were laid up against cabinets, some of which have no underlayment supporting them at the very edges. These tiles are generally a bit loose:

I assume that at the very least I would want to remove these tiles since they could potentially come loose under the new tile, resulting in extreme hassle.

My main questions are:

What should/should not be removed (asbestos tile, underlayment)?

If any asbestos-containing materials are to remain, how do I encapsulate this for safety/health? I've read about products such as Ardex Feather Finish that may be useful in this regard.

How do I bring up all 4 layers to the same level?

How do I create a level/uniform surface without dramatically adding to the height of the finished floor? 1/2" cement backer board would make the height of the kitchen floor 1" higher than the adjacent dining room (which the kitchen is open to across an 8' span), considering 1/4" of thinset and 1/4" tile. Removing the asbestos tile and underlayment could reduce that to 3/4".

I'm also trying to think pretty long-term on this project. I may be in this house for the next 5-10 years and while I expect the new tile to last at least that long, I'm concerned about resale issues and having to disclose the (presumed) existence of asbestos if I do tile over the existing floor. It seems to me that any attempts to take up new tile, years down the road, would disturb any such material under it.

For reference, here is a close-up of the mastic. It is grey/off-white and feels pretty rigid/non-malleable. Any thoughts on the likelihood that it, too, contains asbestos?

Yep. I'm leaning in that direction. Coincidentally, that is my state dept. of health (MN) and I've been studying that page.

I have found cheap asbestos testing, but I'm not sure on the turn-around time and I'd like to get after this soon. I think I will just assume it is asbestos and take the necessary precautions. I know the tiles will come up without issue. The mastic/adhesive worries me a bit. This stuff seems more brittle than I'd expect. Another thing I'm noticing is that the true color of the mastic is more of a caramel brown. The white/gray seems to just be dust and/or part of the tile. I've read that the darker mastics are much more likely to contain asbestos, so this does concern me a bit, depending on how easily that underlayment comes up.

What about patching up those voids/different levels of floor/subfloor? What materials should I be looking to use there? Plywood, OSB, cement backer board? I assume I can just screw any of those down to the subfloor, right?

Also, assuming I remove the tile and underlayment, what should I use as a new underlayment on top of the tongue & groove Douglas fir? A lot of people seem to recommend Ditra in this type of situation. Avoiding extra thickness is a plus to me, but I'm not sure about paying ~ $2/sq. ft. with the Ditra or similar products. I guess another 1/8" with the cement backer board is not that much.

Should I be worried about uncoupling in this situation? The room is only 8' x 12', joists are 16" OC, and the subfloor is pine. The current tile seems very uniform, as do the currently exposed parts of the tongue & groove Douglas fir, from what I can see.

Another "tile over asbestos tile" question (w/ pics)

Thanks for your help, Mike.

I think 1/2" plywood, thinset, 1/4" durock, more thinset, and 1/4" tile on top of my subfloor and tongue & groove flooring is just going to build up the floor way too much, unfortunately. It would be roughly 1 1/4" higher than the adjacent flooring in the dining room, which is open to the kitchen over about a 9' span. I'm not that keen to take the tongue & groove stuff out, either. I assume you recommend the plywood since the t & g boards just aren't dimensionally stable enough?

Reconsidering the Ditra, could I put that directly on top of the t & g?

Another "tile over asbestos tile" question (w/ pics)

Like Bud said--Plywood over the tongue and grove is the only way to do it.

Unless--you remove the tongue and grove--there is 3/4 inch gone--Set your Skill Saw to 3/4 inch--put on gloves and goggles and start ripping it out--You will have it gone in a surprisingly short amount of time.

doing that will eliminate the time consuming job of piecing in the missing areas---along with the risk of the T&G moving at a different rate than the patch work--possibly creating a failure area.

You will now be able to install the plywood as one smooth continuous surface.

Proper prep before setting tile is the key to a safe and successful job.

Another "tile over asbestos tile" question (w/ pics)

Hi Tom wondered if you went ahead and removed the douglas fur or not? If so how did it go? We are in the same position right now. My husband doesn't believe that removal of douglas fur would be so easy. Our house seems to be thoroughly nailed in to place everywhere we look! Our kitchen is 19ft by 8/9ft. If anyone can guess how long it might take to get it up please share.
I realize this post is old so my fingers are crossed.
Thanks